1. Field of the Invention
The present invention relates to an impact-absorbing structure suitable for use as the structure of an aviation vehicle, such as an aircraft or a car, and to a method for producing the same.
This application is based on Japanese Patent Application No. 2009-102091, the content of which is incorporated herein by reference.
2. Description of Related Art
Impact-absorbing structures are used as the structures of traveling bodies, such as aircraft (for example, helicopters, which are rotary-wing aircraft) and cars, to absorb impact in a collision. For example, for helicopters, which are rotary-wing aircraft, an underfloor structure having an impact-absorbing structure has been proposed to assure passenger safety during an forced landing.
As shown in FIG. 7, a web having a pair of face plates 101 opposed to each other with core members 103 and composite-material tubes 105 therebetween. When an impact compression load is applied to the web, fracture propagates in the axial direction of the composite-material tubes 105, whereby the impact energy is absorbed. Furthermore, a plurality of openings are provided or the interlaminar bonding of the composite material is weakened at the peripheral walls at one end of the composite-material tubes disclosed in the aforementioned citation to reduce the failure strength at one end. This accelerates initial failure at this end, reducing an excessive initial reaction force generated when an impact is applied.
However, in the web of FIG. 7, which is generally referred to as a “sandwich panel”, the face plates 101 and the core members 103 are bonded by an adhesive. Therefore, the composite-material tubes 105 are also entirely fixed to the face plates 101 by an adhesive, together with the core members 103.
If the composite-material tubes 105 are entirely fixed to the face plates 101 as in this case, the composite-material tubes 105 are restrained by the face plates 101 when an impact force is applied. As a result, the composite-material tubes 105 fracture subsequent to the failure of the existing structure, such as the face plates, whereby the impact-energy absorption capacity is decreased. Furthermore, even if progressive failure occurs, because the entirety is fixed to the face plates 101, many of the fragments of the fractured impact-absorbing member enter the tubes. This results in a problem in that the effective length of the impact-absorbing member for absorbing the impact energy is reduced.